1. Field of the Invention
This invention relates generally to fluid chamber plugs, and more particularly to a plug for a fluid fill port of a downhole tool.
2. Description of the Related Art
Fluid filled devices, such as various types of downhole tools, frequently require one or more plugs to close off various ports formed in the devices. The primary purpose of such ports is to enable operators to move fluids into and out of the devices. For example, many conventional downhole tools utilize hydraulic fluid to manipulate internal components, such as pistons. The initial requisite volume of hydraulic fluid is introduced into the tool and later drained as necessary during maintenance via the fill port. In addition to fluid movement, fill ports are often used to provide access to components enclosed within the device or tool after the tool is assembled, such as electronic circuitry, sensors or other components.
Various types of plug designs have been used in the oil and gas and other types of industries. One conventional design incorporates a plug with a tapered exterior and a set of tapered threads which are designed to engage a corresponding set of tapered threads in a tapered bore hole in the tool housing. Fluid seal is dependent upon an interference fit between the mating sets of threads. This type of conventional plug design normally becomes less dependable with repeated use due to deformation and wear of the mating sets of threads. Furthermore, this conventional plug design will normally not mount flush with the exterior of the device or downhole tool into which it is inserted. A plug that projects outwardly from the exterior of the device or downhole tool may present a structure which can hang up on the interior surfaces of a wellbore, a coil tubing injector, or other types of internal bore structures. Furthermore, if the portion of the plug projecting from the device impacts other structures during operations, the plug may be damaged and its capability of maintaining a fluid seal degraded.
Another conventional design utilizes a conical shaped plug member that is connected to a threaded hex nut. The connection between the plug member and the hex nut is by way of a flange that is positioned inside the hex nut. The flange is connected to the plug member by a shaft that projects through an opening in one end of the hex nut. A fluid seal is established by plastic deformation of the edges of the port thru-hole by the conical surface of the plug member. The difficulty with this design is the reliance upon plastic deformation of the port structure in order to establish a fluid seal as well as the sheer length of the plug.
Another conventional design incorporates a mandrel which has a threaded section and a smooth section which is fitted with an external O-ring. The O-ring is often positioned on a turned-down outer diameter (xe2x80x9cO.D.xe2x80x9d) portion of the smooth section, and is designed to seal against the inner diameter of a fluid port. High manufacturing cost and complexity are disadvantages associated with this design. In addition, this type of plug may not successfully seal against extremely high pressures and is prone to O-ring extrusion due to the action of high pressure fluid.
Excessive plug length is a disadvantage shared by many conventional designs. Modern downhole tools, particularly those used in coiled tubing applications, frequently have O.D.""s of less than three inches. In tools with such small O.D.""s, the successful scaling of the thickness of the tool housing wall is necessary to accommodate the required internal structures for the tool. Conventional plug designs represent a limitation on the potential scaling of tool wall thickness. In many cases, conventional plugs require a greater wall thickness than is required to resist the working stresses applied to the tool. Accordingly, the tool must either be fabricated with a larger than necessary O.D., or sacrifices in the design of the internal structures of the tool must be made in order to accommodate the wall thickness required by the conventional plug design.
The present invention is directed to overcoming or reducing the effects of one or more of the foregoing disadvantages.
In accordance with one aspect of the present invention, a plug for a housing port that has at least one internal thread and a bottom surface is provided. The plug includes a disk that has an upper surface, a lower surface and an annular groove in the lower surface. The annular groove has an inner wall and a outer wall. An annular seal member is positioned in the annular groove. An annular member is positioned in the annular groove between the annular seal member and the outer wall to retain the annular seal member in the annular groove. A member is provided that has least one external thread for engaging the at least one internal thread of the port whereby rotation of the member in a given direction moves the disk toward and compresses the annular seal member against the bottom surface.
In accordance with another aspect of the present invention, a plug for a housing port that has a bottom surface is provided. The plug includes a disk that has an upper surface, a lower surface and an annular groove in the lower surface. The annular groove has an inner wall and a outer wall. An annular seal member is positioned in the annular groove. An annular member is positioned in the annular groove between the annular seal member and the outer wall to retain the annular seal member in the annular groove. A member is positioned in the port. Means are provided for translating torque applied to the member in a given direction into axial movement of the member toward the bottom surface to move the disk toward and compress the annular seal member against the bottom surface.
In accordance with another aspect of the present invention, a downhole tool is provided. The downhole tool includes a housing that has an internal chamber, a port that has a first portion with at least one internal thread and a second portion that is in communication with the internal chamber and has a reduced diameter portion defining an annular surface. A plug is positioned in the port and has a disk with an upper surface, a lower surface and an annular groove in the lower surface. The annular groove has an inner wall and an outer wall. An elastomeric annular member is positioned in the annular groove. An annular member is positioned in the annular groove between the elastomeric annular member and the outer wall to retain the elastomeric annular member in the annular groove. A member is provided that has at least one external thread for engaging the at least one internal thread of the port whereby rotation of the member in a given direction moves the disk toward and compresses the elastomeric annular member against the annular surface.